Power indication circuit for a processor

ABSTRACT

According to some embodiments, a reference voltage signal initially increases with increases in a processor voltage signal and then decreases with a further increase in the processor voltage signal. Moreover, according to some embodiments a comparator circuit generates a power indication signal when a substantially scaled processor voltage signal exceeds a reference voltage signal.

BACKGROUND

[0001] A circuit may be used to determine when a voltage signaltransitions across a threshold level. For example, a microprocessor or aVery Large-Scale Integration (VLSI) circuit may need to determine when aprocessor voltage signal reaches an acceptable voltage level.

[0002] Traditionally, such a determination is made by a circuit thatuses a stable voltage reference signal. FIG. 1 illustrates traditionalrelationships 100 between a processor voltage signal, a referencevoltage signal, a slightly scaled processor voltage signal, and a powerindication signal at different temperatures.

[0003] Consider first a reference voltage signal 110 generated at 100°Centigrade (C). Note that the reference voltage signal 110 initiallyincreases along with the processor voltage signal (Vcc) That is, thereference voltage signal 100 is about 400 millivolts (mV) when Vcc is400 mV. Above that Vcc, the reference voltage signal 110 begins tostabilize. That is, the rate of increase of the reference voltage signal110 begins to decrease (as compared to Vcc) when Vcc reachesapproximately 600 millivolts (mV). Traditionally, only a limited numberof stable reference voltage values can be produced by such a circuit(e.g., based on diode thresholds, silicon band gap voltages, and/ortransistor thresholds associated with the circuit). In order to generateother reference voltage values, scaling circuits may be used.

[0004] A slightly scaled processor voltage signal 120 at 100° C. isgenerated by scaling down Vcc (e.g., with resistors). As a result, theslightly scaled processor voltage signal 120 rises at a slightly slowerrate as compared to Vcc. For example, the slightly scaled processorvoltage signal 120 illustrated in FIG. 1 reaches approximately 1.0 Volt(V) when Vcc is 1.2 V.

[0005] A power indication signal 130 is then generated when the slightlyscaled processor voltage signal 120 transitions past the referencevoltage signal 110. The power indication signal 130 may indicate, forexample, that Vcc has now reached an acceptable voltage level for aprocessor. The point (e.g., the Vcc) at which the power indicationsignal 130 is generated is determined by the transfer curve of thecircuit. This point may be modified to a desired level by, for example,adjusting the resistance used to scale down the processor voltage.

[0006] There are several disadvantages, however, with the traditionalmethods of generating a power indication for a processor. For example,consider a reference voltage signal 112 that is generated when thetemperature of the circuit is 0° C. Note that this reference voltagesignal 112 levels off at a higher value as compared to the referencevoltage signal 110 at 100° C. Also note that the slightly scaledprocessor voltage signal 122 at 0° C. does not significantly change ascompared to the signal 120 at 100° C. As a result, the power indicationsignal 132 is not generated until a higher Vcc is reached (e.g., thepower indication signal 132 at 0° C. occurs approximately 200 mV afterthe power indication signal 130 at 100° C.). This temperaturesensitivity is undesirable because the pre-determined acceptable voltagelevel for the processor has not actually changed.

[0007] Moreover, because the difference between the reference voltagesignal and the slightly scaled processor voltage signal is small, thecircuit will be sensitive to voltage noise. For example, FIG. 2illustrates traditional relationships 200 between Vcc, a referencevoltage signal 210, a slightly scaled processor voltage signal 220, anda power indication signal 230 when 200 mV of Alternating Current (AC)noise is introduced to a traditional power indication circuit. Note thatthe power indication signal 230 is generated multiple times because theslightly scaled processor voltage signal 220 crosses the referencevoltage signal 210 many times. This result is also undesirable becauseno clear indication of an acceptable voltage level is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 illustrates traditional relationships between a processorvoltage signal, a reference voltage signal, a slightly scaled processorvoltage signal, and a power indication signal at different temperatures.

[0009]FIG. 2 illustrates traditional relationships between a processorvoltage signal, a reference voltage signal, a slightly scaled processorvoltage signal, and a power indication signal when voltage noise isintroduced.

[0010]FIG. 3 is a block diagram of a circuit according to someembodiments.

[0011]FIG. 4 illustrates relationships between a processor voltagesignal, a reference voltage signal, a scaled processor voltage signal,and a power indication signal according to some embodiments.

[0012]FIG. 5 is a flow chart of a method of generating a powerindication signal according to some embodiments.

[0013]FIG. 6 is an example of a curve shaping circuit according to oneembodiment.

[0014]FIG. 7 is an example of a power indication circuit according toone embodiment.

[0015]FIG. 8 illustrates relationships between a processor voltagesignal, a reference voltage signal, a scaled processor voltage signal,and a power indication signal at different temperatures for the circuitsof FIGS. 6 and 7.

[0016]FIG. 9 illustrates relationships between a processor voltagesignal, a reference voltage signal, a scaled processor voltage signal,and a power indication signal when voltage noise is introduced into thecircuits of FIGS. 6 and 7.

DETAILED DESCRIPTION

[0017] Some embodiments are associated with circuits that generate apower indication that reflects when a processor voltage exceeds a“threshold” value. As used herein, a threshold value may be associatedwith, for example, an acceptable voltage level for a processor (e.g., anINTEL® PENTIUM® processor).

[0018] Curve Shaping and Power Indication Circuits

[0019]FIG. 3 is a block diagram of a circuit 300 according to someembodiments. The circuit 300 includes a curve shaping circuit 310 thatreceives a processor voltage signal (i.e., Vcc) and provides a referencevoltage signal that may be used to determine when the processor voltagesignal exceeds a threshold value.

[0020] The curve shaping circuit 310 generates the reference voltagesignal such that the reference voltage signal initially increases withincreases in the processor voltage signal and then decreases withfurther increases in the processor voltage signal.

[0021] Consider FIG. 4 which illustrates relationships 400 between aprocessor voltage signal (Vcc) and a reference voltage signal accordingto some embodiments. As can be seen, the reference voltage signalinitially increases along with the processor voltage signal. The periodof this increase may be associated with, for example, a voltagethreshold of a transistor in the curve shaping circuit 310.

[0022] The reference voltage signal then decreases with a furtherincrease in the processor voltage signal. Note that the referencevoltage signal may decrease substantially with a further increase in theprocessor voltage signal. For example, the reference voltage signal mayrise to 500 mV before stabilizing at 350 mV. This may be achieved, forexample, by clamping the reference voltage signal to a voltage thresholdof a diode in the curve shaping circuit 310.

[0023] According to some embodiments, the curve shaping circuit 310generates the reference voltage signal such that the reference voltagesignal will exceed a scaled threshold value before stabilizing at thescaled threshold value. Note that the scaled threshold value does notneed to equal an acceptable voltage level for the processor (e.g., ifthe acceptable voltage level for a processor is 1 V the scaled thresholdvalue might be 350 mV).

[0024] Referring again to FIG. 3, the circuit 300 also includes a powerindication circuit 320 that receives: (i) the processor voltage signal,and (ii) the reference voltage signal generated by the curve shapingcircuit 310. In particular, the power indication circuit 320 includes ascaling circuit 330 that generates a scaled processor voltage signalbased on the processor voltage signal. The scaling circuit 330 maycomprise, for example, a variable resistance divider to substantiallyscale down the processor voltage signal (e.g., by generating Vcc/x). Asused herein, a “substantially” scaled down processor voltage signal maycomprise a signal that has been reduced by at least fifty percent.

[0025] The power indication circuit 320 further includes a comparatorcircuit 340 that generates a power indication signal when the output ofthe scaling circuit 340 (e.g., Vcc/x) exceeds the reference voltagereceived from the curve shaping circuit 310.

[0026] Referring again to FIG. 4, which further illustratesrelationships between the processor voltage signal, the referencevoltage signal, and a scaled processor voltage signal according to someembodiments. As can be seen, the scaled processor voltage signal risesalong with the processor voltage signal—although at a slower rate (e.g.,the scaled processor voltage signal might represent Vcc/3). Moreover,the comparator circuit 340 generates a power indication signal when thescaled processor voltage signal exceeds the reference voltage signal(e.g., as represented by an “X” in FIG. 4).

[0027] Note that the reference voltage signal and the scaled processorvoltage signal may reduce a temperature sensitivity of the powerindication signal. Consider, for example, the case wherein the scalingcircuit 320 reduces the processor voltage by fifty percent in order togenerate the scaled processor voltage. In this case, the referencevoltage signal provided by the curve shaping circuit 310 may stabilizeat a value equal to half of an acceptable processor voltage level. As aresult, the comparator circuit 340 generates the power indication signalwhen the scaled processor voltage signal exceeds the stabilizedreference voltage signal (i.e., Vcc/2 will exceed half of the acceptableprocessor voltage value—and thus Vcc will exceed the acceptableprocessor voltage value). Because the reference voltage signal and theprocessor voltage signal have been substantially scaled down, thetemperature sensitivity of the circuit 300 may be correspondinglyreduced (e.g., by fifty percent) as compared to a traditional circuit.An example of reduced temperature sensitivity is described with respectto FIG. 8.

[0028] Moreover, the reference voltage signal and the scaled processorvoltage signal may reduce a noise sensitivity of the power indicationsignal. Note that the scaled processor voltage signal increases at aslower rate as compared to Vcc. The reference voltage signal, on theother hand, initially increases directly with Vcc and then decreases andstabilizes at a scaled threshold value. As a result, the referencevoltage signal may generally differ from the scaled processor voltagesignal by an amount greater than that associated with a traditionalcircuit. Thus, the effect of noise (e.g., the likelihood that the scaledprocessor voltage signal will transition across the reference voltagesignal multiple times) may be reduced. An example of reduced noisesensitivity is described with respect to FIG. 9.

[0029] Power Indication Method

[0030]FIG. 5 is a flow chart of a method of generating a powerindication according to some embodiments. The flow chart does not implya fixed order to the actions, and embodiments of the present inventionmay be practiced in any order that is practicable. The method may beassociated with, for example, the circuit 300 illustrated in FIG. 3.

[0031] At 502, a reference voltage signal is generated. For example, thecurve shaping circuit 310 may generate the reference voltage signal suchthat the reference voltage signal initially increases with increases ina processor voltage signal and then decreases with a further increase inthe processor voltage signal.

[0032] At 504, a scaled processor voltage signal is generated based onthe processor voltage signal. For example, the scaling circuit 320 mayreduce the processor voltage signal by fifty percent.

[0033] If the scaled processor voltage signal exceeds the referencevoltage signal at 506, a power indication is generated at 508. The powerindication may represent, for example, that an acceptable voltage levelfor a processor has been achieved. If the scaled processor voltagesignal does not exceed the reference voltage signal at 506, no powerindication is generated at 510.

EXAMPLE

[0034]FIG. 6 is an example of a curve shaping circuit 600 according toone embodiment. The curve shaping circuit 600 includes a processorvoltage input line (“CPU_VCC”) to receive a processor voltage signal anda reference voltage output line (“REFERENCE_OUT”) to provide a referencevoltage signal (e.g., to the power indication circuit described withrespect to FIG. 7).

[0035] The curve shaping circuit 600 generates the reference voltagesignal such that the reference voltage signal initially increases withincreases in the processor voltage signal and then decreases (e.g.,substantially decreases) and eventually stabilizes with furtherincreases in the processor voltage signal. The period of the increasemay be associated with, for example, a voltage threshold of a transistorin the curve shaping circuit 600. The decrease and stabilization of thereference voltage signal may be achieved, for example, by clamping thereference voltage signal to a voltage threshold of a diode 610 in thecurve shaping circuit 600.

[0036]FIG. 7 is an example of a power indication circuit 700 accordingto one embodiment. The power indication circuit 700 includes a processorvoltage input line (“CPU_VCC”) to receive a processor voltage signal anda reference voltage input line (“REFERENCE_OUT”) to receive a referencevoltage signal (e.g., from the curve shaping circuit 600 described withrespect to FIG. 6). The power indication circuit 700 further includes apower indication output line to provide a power indication signal (e.g.,“PWR_GOOD”).

[0037] The power indication circuit 700 includes a variable resistancedivider 710 to substantially scale down the processor voltage signal(e.g., to generate Vcc/x). The power indication circuit 700 furtherincludes a comparator that generates the power indication signal whenthe output of the variable resistance divider 710 exceeds the referencevoltage received from the curve shaping circuit 600.

[0038]FIG. 8 illustrates relationships 800 between a processor voltagesignal (Vcc), a reference voltage signal, a scaled reference voltagesignal, and a power indication signal at different temperatures for thecircuits of FIGS. 6 and 7.

[0039] Consider first the reference voltage signal 810 generated by thecurve shaping circuit 600 at 100° C. Note that the reference voltagesignal 810 initially increases along with the processor voltage signal,then decreases, and finally stabilizes at about 300 mV after Vcc reachesabout 800 mV.

[0040] A scaled processor voltage signal 820 at 100° C. is generated bysubstantially scaling down the processor voltage signal. As a result,the scaled processor voltage 820 rises at a substantially slower rate ascompared to Vcc. For example, the scaled processor voltage signal 820illustrated in FIG. 8 is approximately 300 mV when Vcc is 800 mV.

[0041] A power indication signal 830 is then generated when the scaledprocessor voltage signal 820 transitions past the reference voltagesignal 810. The power indication signal 830 may indicate, for example,that Vcc has now reached an acceptable voltage level for a processor.

[0042] Note that the curve shaping circuit 600 and the power indicationcircuit 700 may substantially reduce temperature sensitivity as comparedto traditional circuits. For example, consider a reference voltagesignal 812 generated by the curve shaping circuit 600 when thetemperature of the circuit is 0° C. In this case, the reference voltagesignal 812 eventually stabilizes at about 350 mV (instead of 300 mV).Moreover, the power indication signal 832 at 0° C. is generated about100 mV after the Vcc at which it would have been generated at 100° C.(as compared to the 200 mV difference associated with FIG. 1). That is,because the reference voltage signals and the processor voltage signalshave been substantially scaled down, the temperature sensitivity hasbeen correspondingly reduced.

[0043]FIG. 9 illustrates relationships 900 between a processor voltagesignal (Vcc), a reference voltage signal 910, a scaled reference voltagesignal 920, and a power indication signal 930 when 200 mV of AC noise isintroduced into the circuits of FIGS. 6 and 7. Note that the scaledprocessor voltage 920 increases at a slower rate than Vcc. The referencevoltage signal 910, on the other hand, initially increases directly withVcc and then decreases and stabilizes at a scaled threshold value (e.g.,around 300 mV). As a result, the reference voltage signal 910 maygenerally differ from the scaled processor voltage signal 920 by anamount greater than that associated with a traditional circuit. Thus,the effect of noise may be reduced and the scaled processor voltagesignal 920 may transition across the reference voltage signal 910 fewertimes as compared to a traditional circuit (e.g., as compared to FIG.2).

[0044] Thus, embodiments may substantially reduce temperature and noisesensitivity for a power indication signal as compared to traditionalcircuits, and a more robust processor may be provided.

[0045] Additional Embodiments

[0046] The following illustrates various additional embodiments. Thesedo not constitute a definition of all possible embodiments, and thoseskilled in the art will understand that many other embodiments arepossible. Further, although the following embodiments are brieflydescribed for clarity, those skilled in the art will understand how tomake any changes, if necessary, to the above description to accommodatethese and other embodiments and applications.

[0047] Note that FIGS. 6 and 7 merely illustrate examples of circuitsthat might be provided according to one embodiment, and that any numberof other circuits could instead be used. Moreover, the power indicationsignal may represent a condition other than an acceptable processorvoltage level (e.g., a power indication may represent that a voltagelevel is no longer acceptable). Similarly, although particular voltagelevel values are discussed herein, embodiments may be provided for anyvoltage level values.

[0048] The several embodiments described herein are solely for thepurpose of illustration. Persons skilled in the art will recognize fromthis description other embodiments may be practiced with modificationsand alterations limited only by the claims.

What is claimed is:
 1. A circuit, comprising: a processor voltage inputline to receive a processor voltage signal; a reference voltage outputline to provide a reference voltage signal associated with adetermination of when the processor voltage signal exceeds a thresholdvalue; and a curve shaping circuit to generate the reference voltagesignal such that the reference voltage signal initially increases withincreases in the processor voltage signal and then decreases with afurther increase in the processor voltage signal.
 2. The circuit ofclaim 1, wherein the threshold value is associated with an acceptablevoltage level for a processor.
 3. The circuit of claim 1, wherein thereference voltage signal decreases substantially with a further increasein the processor voltage signal.
 4. The circuit of claim 1, wherein thereference voltage signal follows the processor voltage signal up to alevel associated with a transistor voltage threshold.
 5. The circuit ofclaim 1, wherein the reference voltage is clamped to a diode voltagethreshold.
 6. The circuit of claim 1, further comprising: a referencevoltage output line to provide the reference voltage signal.
 7. Thecircuit of claim 1, further comprising: a power indication circuit,comprising: a processor voltage input line to receive the processorvoltage signal, a reference voltage input line to receive the referencevoltage signal, and a comparator circuit to generate a power indicationsignal based on the processor voltage signal and the reference voltagesignal.
 8. The circuit of claim 7, further comprising: a scaling circuitto generate a scaled processor voltage signal, wherein the comparatorcircuit is to generate the power indication when the scaled processorvoltage signal exceeds the reference voltage signal.
 9. The circuit ofclaim 8, wherein the scaling circuit comprises a variable resistancedivider to substantially scale down the processor voltage signal. 10.The circuit of claim 9, wherein the reference voltage signal and thescaled processor voltage signal substantially reduces a temperaturesensitivity of the power indication signal.
 11. The circuit of claim 9,wherein the reference voltage signal and the scaled processor voltagesignal substantially reduces a noise sensitivity of the power indicationsignal.
 12. The circuit of claim 7, wherein the power indication circuitfurther comprises: a power indication output line to provide the powerindication signal.
 13. A circuit, comprising: a processor voltage inputline to receive a processor voltage signal; a reference voltage outputline to provide a reference voltage signal associated with adetermination of when the processor voltage signal exceeds a thresholdvalue; and a curve shaping circuit to generate the reference voltagesignal such that the reference voltage signal will exceed a scaledthreshold value before stabilizing at the scaled threshold value. 14.The circuit of claim 13, wherein the threshold value is associated withan acceptable voltage level for a processor.
 15. A circuit, comprising:a processor voltage input line to receive a processor voltage signal; avariable resistance divider to substantially scale down the processorvoltage signal to generate a scaled processor voltage signal; areference voltage input line to receive a reference voltage signal; acomparator circuit to generate a power indication signal when the scaledprocessor voltage signal exceeds the reference voltage signal.
 16. Thecircuit of claim 15, wherein the reference voltage signal initiallyincreases with increases in the processor voltage signal and thendecreases with a further increase in the processor voltage signal
 17. Aprocessor, comprising: a reference voltage circuit, comprising: aprocessor voltage input line to receive a processor voltage signal, areference voltage output line to provide a reference voltage signal, anda curve shaping circuit to generate the reference voltage signal suchthat the reference voltage signal initially increases with increases inthe processor voltage signal and then decreases with a further increasein the processor voltage signal; and a power indication circuit,comprising: a processor voltage input line to receive the processorvoltage signal, a scaling circuit to generate a scaled processor voltagesignal, a reference voltage input line coupled to reference voltageoutput line of the reference voltage circuit, and a comparator circuitto generate a power indication signal when the scaled processor voltagesignal exceeds the reference voltage signal.
 18. The processor of claim17, wherein the power indication signal is associated with an acceptablevoltage level for the processor.
 19. A method, comprising: generating areference voltage signal such that the reference voltage signalinitially increases with increases in a processor voltage signal andthen decreases with a further increase in the processor voltage signal;generating a scaled processor voltage signal based on the processorvoltage signal; and generating a power indication signal when the scaledprocessor voltage signal exceeds the reference voltage signal.
 20. Themethod of claim 19, wherein the power indication signal is associatedwith an acceptable voltage level for a processor.